Somatomedin activity and growth hormone levels in body fluids of the fetal pig: effect of chronic hyperinsulinaemia

Abstract

Chronic hyperinsulinaemia in the presence of euglycaemia was obtained in pig fetuses between 90 and 104 days gestational age (term is 114 days) by the implantation of insulin-filled osmotic minipumps. At 104 days these fetuses were compared with both saline-implanted controls and with unoperated fetuses from the same sows. Mean plasma GH levels were the same in all three treatment groups and were much greater than in the maternal peripheral venous circulation. Levels of GH in amniotic fluid were low, and even lower levels were measured in lung fluid. Glucose and protein levels were also lower in amniotic fluid than in plasma and lower still in lung fluid. In contrast, somatomedin activity was higher in amniotic and lung fluids than in fetal plasma and, when expressed relative to protein content, was highest in lung fluid. Insulin-treated fetuses had significantly (P less than 0.05) higher levels of somatomedin activity than control fetuses, but despite this were neither longer nor heavier than control fetuses. From these data it is concluded that neither insulin nor somatomedin directly affect fetal growth.

Tissue and Serum Concentrations of Somatomedin-C/Insulin-Like Growth Factor I in Fetal Rats Made Growth Retarded by Uterine Artery Ligation

“…It may be that insulin in the fetus serves "to maintain a favorable homeostatic environment" (4), or alternately insulin may stimulate fetal somatomedin production. Both fetal rabbits and pigs respond to hyperinsulinemia with elevation of somatomedin bioactivity (42)(43)(44). However, our observations of an association between insulin and serum Sm-C/IGF I, but not with liver Sm-C/IGF I, do not support a strong direct role for insulin in the control of Sm-C/IGF I synthesis.…”

Human fetal and adult chondrocytes. Effect of insulinlike growth factors I and II, insulin, and growth hormone on clonal growth.

“…Administration of longacting insulin to hypophysectomized rats leads to increase in body weight and length (32). Intrauterine application of insulin, however, has failed to provoke an increase of fetal body length in fetal rhesus monkeys and pigs (1 1,33). In our study, insulin, even at supraphysiological concentrations, did not significantly promote clonal growth of either human fetal or adult chondrocytes.…”

Enteral IGF-I enhances fetal growth and gastrointestinal development in oesophageal ligated fetal sheep

“…With the accompanying increase in amniotic fluid volume, this resulted in a total amniotic fluid IGF-I content approximately 10-fold higher than that of the sham operated control animals. IGF-I enters amniotic fluid from oral and pulmonary secretions (Spencer et al 1983, Hill et al 1984, and from fetal urine. Since failure of clearance by swallowing is likely to apply equally to the saline and IGF-I groups in this experiment, the higher amniotic fluid levels in the IGF-I group suggests increased IGF-I concentrations in fluids entering the amniotic sac.…”